This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For patients who have suffered neurotrauma due to traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH), it is of utmost importance to monitor changes in their cerebral blood flow (CBF) and oxygenation due to risk of ischemia in injured parts of the brain. In this study, we used a hybrid diffuse optical device to characterize the hemodynamic effects of head position and hyperoxia on neurotrauma patients, thereby assessing their cerebral autoregulation. The device is being developed as a portable, relatively inexpensive bedside monitor that employs non-invasive, continuous optical techniques to measure changes in CBF as well as deoxy- and oxyhemoglobin concentrations.